BRASILIA, May 22 (Reuters) - Brazil is suing the world's largest cigarette makers, British American Tobacco Plc and Philip Morris International, in a landmark case aimed at recovering the public health treatment costs of tobacco-related diseases over the last five years.

The Brazilian solicitor general's office, known as the AGU, announced the lawsuit late on Tuesday against the two multinational companies and their Brazilian subsidiaries, who produce most of the cigarettes sold in the country.

The suit seeks to recover the cost of treating patients for 26 illnesses related to smoking tobacco or coming into contact with cigarette smoke, the AGU said in a statement.

Tobacco is the leading cause of preventable death in Brazil. It kills over 156,000 each year from related diseases, costing the healthcare system about 57 billion reais ($14.1 billion), according to a statement from Bloomberg Philanthropies.

The value of the costs that the government seeks to recover will be calculated at a later date if it wins the lawsuit, filed in the southern city of Porto Alegre, the AGU said.

"Since the profit from this business is sent abroad, it is fair that these multinational companies pay for this responsibility they have left to Brazilian society," prosecutor Davi Bressler said in the statement.

The lawsuit was heralded as historic by groups that advocate for reducing tobacco consumption.

"The suit is the first of its kind for Brazil and a significant step toward holding the two major tobacco companies who do business in Brazil and their parent companies responsible for the enormous financial and health burdens caused by tobacco use," the Washington-based Campaign for Tobacco-Free Kids said.

Michael Bloomberg, the World Health Organization's global ambassador for noncommunicable diseases, said Brazil spends billions every year to treat tobacco-related illness "and tobacco companies must be held accountable."

The international companies, through their subsidiaries, Souza Cruz Ltda, Philip Morris Brasil Industria e Comercio Ltda and Philip Morris Brasil SA, produce about 90% of the cigarettes sold in Brazil, the AGU statement said.

Philip Morris Brasil said it had not been informed of the case and would hold off from commenting on the lawsuit.

BAT's Souza Cruz said it had not been given access to the court documents. (Reporting by Anthony Boadle, editing by G Crosse and Bernadette Baum)

Our global editorial team of more than 50 journalists and about 250 freelancers covers the world’s under-reported stories at the heart of aid, development, women’s and LGBT+ rights, human trafficking, property rights, and climate change.